Advanced: Changing refresh type for a materialized view

When you create a materialized view its refresh type is manual. However, you can change it to immediate. You can also change
an immediate view back to manual again.

Prerequisites

You must be a user with DBA authority or be the owner of the view and all of the tables it references.

To change from manual to immediate, the view must be in an uninitialized state (contain no data). If the view was just created
and has not yet been refreshed, it is uninitialized. If the materialized view has data in it, you must execute a TRUNCATE
statement on it to return it to an uninitialized state before you can change it to immediate. The materialized view must also
have a unique index, and must conform to the restrictions required for an immediate view.

An immediate view can be changed to manual at any time without any additional steps other than changing its refresh type.